FAQ: Powervault

Posted On 04-09-2017

Powervault can reduce homeowners’ electricity bills by up to 20% by storing solar energy during the day and discharging it when needed. Powervault can also charge from the grid, which means it can store cheap, off-peak (eg. Economy 7) electricity. UK homeowners on time-of-use-tariffs like Economy 7 can benefit by saving an additional 10% – 15% on their electricity bills, (saving up to 35% in total). When new smart tariffs are launched, with a greater arbitrage between on- and off-peak tariffs, the savings from storing cheap electricity from the grid for UK homeowners will be much larger. Powervault is forward compatible with smart tariffs.

Every two weeks Libra Energy will post new FAQ’s on the Powervault.

WHEN MY LEAD ACID BATTERIES FAIL CAN I REPLACE THEM WITH THE LATEST LITHIUM-ION BATTERY TECHNOLOGY?

Yes, when the Lead Acid batteries reach the end of their useful life, (typically within 3 – 7 years’ time depending on the type of Lead Acid battery you have chosen), you can purchase the latest Lithium-ion battery technology. If Lithium-ion battery price forecasts are anything to go by then, in c. 5 years’ time, Lithium-ion cells will cost half what they are now. You can therefore buy a Lead Acid Powervault now with a lower up-front cost and begin benefiting from reduced electricity bills, before upgrading to Lithium-ion technology when the Lead Acid batteries reach the end of their life and the price of Lithium-ion cells has halved.

WHAT TYPE OF BATTERY TECHNOLOGY IS USED INSIDE POWERVAULT?

Powervault can accommodate Lithium-ion technology and two different types of Lead Acid battery:

Lead Acid – AGM

The AGM Powervaults offer customers the most affordable way to store solar energy in their home. Customers can store from 3kWh to 4kWh using the AGM batteries, which can easily be replaced – either with a new set of AGM or our Lithium-ion battery packs – at the end of their life. Designed to: store and use free solar energy more efficiently.

The Tubular Gel Powervaults are designed to help customers store and use free solar energy and cheap, off-peak electricity (e.g. Economy 7) more efficiently. The Tubular Gel Powervaults are heavy-duty and can cycle more than once per day. Customers can store from 2.5kWh to 4kWh using the Tubular Gel batteries, which can easily be replaced – either with a new set of Tubular Gel or our Lithium-ion battery packs – at the end of their life.

Designed to: store and use free solar energy and off-peak electricity more efficiently

Benefits: heavy-duty and long-lasting yet cheaper than Lithium-ion

Capacities available: 2.5kWh, 4kWh

Charger / Inverter: 1.2kW / 1.6kVA

Life cycles: >1,800

Warranty: 5 years

Lithium-ion Phosphate

The Lithium-ion (LiFePO4) Powervaults are designed to help customers store and use free solar energy and cheap, off-peak electricity (e.g. Economy 7) more efficiently. The Lithium-ion Powervaults are heavy-duty, long-lasting and can cycle more than once per day. Customers can store from 2kWh to 6kWh using the Lithium-ion battery packs, which can easily be replaced or added to.

Designed to: store and use free solar energy and off-peak electricity more efficiently

Benefits: high energy density, high efficiency, heavy-duty and long-lasting

Capacities available: 2kWh, 4kWh, 6kWh

Charger / Inverter (2kWh): 0.8kW / 0.8kVA

Charger / Inverter (4/6kWh): 1.2kW / 1.6kVA

Life cycles: >4,000

Warranty: 10 years

WHAT ARE THE PROS AND CONS OF LEAD ACID VS LITHIUM-ION BATTERY TECHNOLOGIES?

Lead Acid technologies have a lower up-front cost but require more frequent replacement than Lithium-ion. The Lead Acid batteries used in Powervault are designed for consumer use, and are sealed; some customers prefer Lead Acid batteries as they are a tried and tested technology with a strong reputation for safety.

While 100% of the lead in Powervault’s Lead Acid batteries is recyclable, lead has historically had a poor environmental reputation. Lithium-ion technologies are currently higher cost but the batteries last proportionally longer; the technology is now maturing and costs are falling but there are environmental concerns surrounding their disposal.

HOW LONG WILL POWERVAULT’S BATTERIES LAST?

Lead acid

Powervault’s Lead Acid batteries are designed to have a lifetime of 3 – 7 years (depending on the type of Lead Acid battery you choose) after which they will need to be replaced; at that stage you can either replace them with a new set of Lead Acid batteries (cost: £350 – £700) or purchase the latest Lithium-ion battery technology.

Lithium-ion

Powervault’s Lithium-ion batteries can offer you over 4,000 cycles and are estimated to last 11 – 13 years.

HOW LONG WILL POWERVAULT STORE POWER FOR?

Powervault is designed to charge and discharge once every 24 hours. However, if there is no demand from appliances in your home during the day then Powervault will not discharge.

CAN I CHARGE POWERVAULT DURING OFF-PEAK OR ‘ECONOMY 7’ TARIFFS?

Powervault can be programmed to charge during off-peak or ‘Economy 7’ tariffs to store cheap electricity. This can be set up via Powervault’s online customer portal.

WHEN MY LEAD ACID BATTERIES FAIL CAN I REPLACE THEM WITH THE LATEST LITHIUM-ION BATTERY TECHNOLOGY?

Yes, when the Lead Acid batteries reach the end of their useful life, (typically within 3 – 7 years’ time depending on the type of Lead Acid battery you have chosen), you can purchase the latest Lithium-ion battery technology. If Lithium-ion battery price forecasts are anything to go by then, in c. 5 years’ time, Lithium-ion cells will cost half what they are now. You can therefore buy a Lead Acid Powervault now with a lower up-front cost and begin benefiting from reduced electricity bills, before upgrading to Lithium-ion technology when the Lead Acid batteries reach the end of their life and the price of Lithium-ion cells has halved.

WILL POWERVAULT AFFECT MY FEED-IN TARIFF PAYMENTS?

No, Powervault will not have any effect on your Feed-in tariff, which you will continue to receive in full. You will benefit from a reduced electricity bill.

HOW MUCH CAN POWERVAULT SAVE ME PER YEAR?

Customers with solar PV panels save around 50% through self-consumption. Powervault can increase this saving to 70%. For home owners with solar panels and Economy 7 tariffs, this saving can be increased further to 80%. However, properties with high consumption during the day / off-peak times or with small solar PV installations may save less than this.

WHY IS POWERVAULT SIZED AND SPECIFIED LIKE IT IS?

Powervault is designed to be “just right” for UK homes. As a British company we will continue to listen to what customers want. However, there are good rationale for the sizing and specification we have chosen:

Charger & Inverter

The size of the charger and inverter is designed to get all of the kWh in/out of the battery on a “trickle” basis every 24 hours. A larger inverter gets the energy out faster but reduces discharge efficiency. A larger inverter/charger will also cost more than the additional saving it would provide.

Battery sizing

Battery size has been chosen to maximise battery usage over the year. A larger battery would only be fully used on a small number of days.

Conclusion

Since the inverter and battery are costly components driven by size, it does not make sense to us to over-size them. Our ethos is to try to maximise use of the inverter and batteries. So rather than trying to power the whole of your oven or iron, we are, instead, offsetting a percentage of power consumption the whole time, thereby providing the same overall benefit.

WILL POWERVAULT BE COMPATIBLE WITH MY SOLAR PV SYSTEM AND INVERTER?

Powervault is AC-connected and is therefore compatible with all inverters and solar PV systems. It is very easy to retro-fit to your existing solar PV system.

ARE DC CONNECTED SYSTEMS MORE EFFICIENT?

Owing to the tariff structures and metering in the UK, AC-connected system can charge for free. Inefficiencies in battery charging have no impact on the Feed-in tariff for AC-connected systems. By making the system AC-connected, Powervault is also far easier to install and is universally compatible with all solar PV systems. DC-connected systems can charge behind the Generation Meter, however you will notice a reduction in your Feed-in tariff as any inefficiencies in the DC-connected system will result in a reduction in the Generation Meter reading.

WHAT HAPPENS TO POWERVAULT IN A POWER CUT?

Powervault is able to provide an uninterrupted power supply to appliances plugged into Powervault’s emergency power socket on the front of the unit, (provided there is energy stored in the batteries at that time). It provides a maximum continuous power output of 1200VA; Powervault is consequently unable to power high-energy appliances such as a kettle or tumble-dryer during a power cut.

HOW WILL I BE ABLE TO SEE HOW POWERVAULT IS WORKING?

Powervault’s intuitive light display system indicates how much power is stored in the system and whether the system is charging or discharging. Powervault owners are also able to log-in to an online customer portal to see how their Powervault is performing. The online portal tracks the home’s electricity consumption and records home electricity demand, storage, discharge and export over time.

Powervault has 5 different LED colours, which signify the following:

Green = charging

Blue = discharging

Yellow = emergency power socket mode: no Grid

Dark Blue = idle

Red = system fault

WHY IS POWERVAULT SIZED AND SPECIFIED LIKE IT IS?

Powervault is designed to be “just right” for UK homes. As a British company we will continue to listen to what customers want. However, there are good rationale for the sizing and specification we have chosen:

Charger & Inverter

The size of the charger and inverter is designed to get all of the kWh in/out of the battery on a “trickle” basis every 24 hours. A larger inverter gets the energy out faster but reduces discharge efficiency. A larger inverter/charger will also cost more than the additional saving it would provide.

Battery sizing

Battery size has been chosen to maximise battery usage over the year. A larger battery would only be fully used on a small number of days.

Conclusion

Since the inverter and battery are costly components driven by size, it does not make sense to us to over-size them. Our ethos is to try to maximise use of the inverter and batteries. So rather than trying to power the whole of your oven or iron, we are, instead, offsetting a percentage of power consumption the whole time, thereby providing the same overall benefit.